This invention relates to the field of guidewires for advancing intraluminal devices such as stent delivery catheters, balloon dilatation catheters, atherectomy catheters and the like within body lumens.
In a typical percutaneous coronary procedure, a guiding catheter having a pre-formed distal tip is percutaneously introduced into a patient""s peripheral artery, e.g. femoral or brachial artery, by means of a conventional Seldinger technique and advanced therein until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. A guidewire is first advanced by itself through the guiding catheter until the distal tip of the guidewire extends beyond the arterial location where the procedure is to be performed. Then a rail type catheter, such as described in U.S. Pat. No. 5,061,395 (Yock) and the previously discussed McInnes, et al., is mounted onto the proximal portion of the guidewire which extends out of the proximal end of the guiding catheter which is outside of the patient. The catheter is advanced over the guidewire, while the position of the guidewire is fixed, until the operative means on the rail type catheter is disposed within the arterial location where the procedure is to be performed. After the procedure the intravascular device may be withdrawn from the patient over the guidewire or the guidewire repositioned within the coronary anatomy for an additional procedure.
A guidewire may also be used in conjunction with the delivery of an intracorornary stent. One method and system involves disposing a compressed or otherwise small diameter stent about an expandable member such as a balloon on the distal end of a catheter, advancing the catheter through the patient""s vascular system over a guidewire until the stent is in the desired location within a blood vessel and then expanding the expandable member on the catheter to expand the stent within the blood vessel. The dilated expandable member is then contracted and the catheter withdrawn, leaving the expanded stent within the blood vessel, holding the passageway thereof open. This latter method and system can be used concurrently with balloon angioplasty or subsequent thereto.
Further details of guidewires, and devices associated therewith for various interventional procedures can be found in U.S. Pat. No. 4,748,986 (Morrison et al.); U.S. Pat. No. 4,538,622 (Samson et al.); U.S. Pat. No. 5,135,503 (Abrams); U.S. Pat. No. 5,341,818 (Abrams et al.); and U.S. Pat. No. 5,345,945 (Hodgson, et al.) which are hereby incorporated herein in their entirety by reference thereto.
Conventional guidewires for angioplasty, stent delivery, atherectomy and other intravascular procedures usually comprise an elongate core member with one or more tapered segments near the distal end thereof. A flexible body member, such as a helical coil or a tubular body of polymeric material, is typically disposed about the distal portion of the core member. A shapable member, which may be the distal extremity of the core member or a separate shapeable ribbon which is secured to the distal extremity of the core member extends through the flexible body and is secured to the distal end of the flexible body by soldering, brazing or welding, or an adhesive in the case of polymeric flexible bodies which forms a rounded distal tip. The leading tip is highly flexible and will not damage or perforate the vessel and the portion behind the distal tip is increasingly stiff which better supports a balloon catheter or similar device.
The shapeable member or ribbon of a typical guidewire is a small diameter wire which has been flattened to a constant transverse profile. Flattening of the shapable member facilitates the shapability of the member, however, a shapable member having a constant transverse profile or flexibility can be subject to prolapse during use. Prolapse occurs when the shapable member gets bent back on itself in a constrained lumen and is difficult to straighten out with proximal manipulation. One method of preventing prolapse or reducing the occurrence thereof is to have increased stiffness at a proximal end of a shapable member. This has been done with incremental steps in the shapable member with thinner more flexible steps distally creating greater flexibility distally. However, the use of incremental steps can cause abrupt changes in flexibility of the shapable member which can be detrimental to smooth tracking and performance of the guidewire. What has been needed is a guidewire with a shapeable member at the distal section that is continuously varied in flexibility and maintains a shapeable character. The present invention satisfies these and other needs.
The present invention is directed to a guidewire having an elongate core member with a proximal section and a distal section. The distal section preferably has at least one flexible segment with two or more opposed faces that are parallel or distally tapered in essentially the same or mirror image relationship to each other. The distal section may also have one or more tapered segments which have typical distally decreasing tapers with substantially round transverse cross sections.
Preferably the flexible segment is disposed at a distal end of the distal section where it can perform the function of a shapeable member. The flexible segment has a length typically ranging from about 1 to about 12 cm, preferably about 2 to about 10 cm, although longer segments may be used. The flexible segment provides a controlled longitudinal variation and transition in flexibility of the core segment. A flexible body member having a proximal end and a distal end is typically disposed about and attached to the distal section of the elongate core member. A flexible body member, such as a helical coil, polymer jacket, or the like, surrounds and covers at least a portion of the distal section of the elongate core member. The proximal end of the helical coil or flexible body typically is secured to the distal section of the elongate core member. Depending on the selected lengths of the helical coil and the flexible segment or shapeable member, the junction of the proximal end of the coil to the core may be at an intermediate position on the distal section or may be at an intermediate position on the flexible segment or anywhere in between.
In one preferred embodiment of a guidewire having features of the invention, the distal section of the core member has at least one flexible segment with at least two opposed tapered faces tapering distally over the length of the flexible segment to a smaller transverse separation. Optionally, the opposed tapered faces may be mirror images and parallel as well as distally tapered. In addition, the tapered faces may have either a substantially straight or curved longitudinal profile. Other than the flexible segment, the construction of the guidewire is similar to the guidewire discussed above with a flexible body member disposed about at least a portion of the distal section and is secured thereto. The proximal section of the elongate core member is nominally round in cross section and preferably with a constant diameter and said round cross section preferably extends distally to a proximal end of the flexible segment disposed on the distal section of the core. The flexible segment may be disposed anywhere on the distal section, but preferably is disposed at a distal end of the distal section, serving as a shapable member.
The taper geometry of the flexible segment may be modeled mathematically. Specific taper or face angles or contours may be selected in keeping with the principles and spirit of the invention to achieve optimum performance for specific usage requirements. These and other advantages of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying exemplary drawings.